AUTHOR=Liu Jian-Xun , Gao Ting , Wang Xu , Jin Hong-Bin , Deng Wei-Qiang , Liu Tai-Yang , Yu Tong-Pu 

TITLE=High-flux positron generation via the ultra-intense laser irradiating density-modulated plasmas

JOURNAL=Frontiers in Physics

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2022.1052654

DOI=10.3389/fphy.2022.1052654

ISSN=2296-424X

ABSTRACT=<p>To investigate plasma density during the Breit–Wheeler positron generation, a comparative study of four plasma targets is performed <italic>via</italic> the PIC (particle-in-cell) code EPOCH. When an ultra-intense laser (<inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>2.8</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>23</mml:mn></mml:msup><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi mathvariant="normal">W</mml:mi><mml:mi mathvariant="normal">c</mml:mi><mml:mi mathvariant="normal">m</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>) is incident, more positrons with high energy are generated in the increasing density plasmas. The positron yield is already <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1.5</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>8</mml:mn></mml:msup></mml:mrow></mml:math></inline-formula> with a cutoff energy of 2 GeV at <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">t</mml:mi><mml:mo>=</mml:mo><mml:mn>37</mml:mn><mml:msub><mml:mi mathvariant="normal">T</mml:mi><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula>. It is demonstrated that increasing density plasmas will enhance gamma photon radiation and positron generation. In increasing density plasmas, under-dense plasmas favor electron acceleration, and over-dense plasmas will induce laser reflection. Cross sections of the Compton back-scattering and the BW positron generation are both increased <italic>via</italic> high-energy electrons colliding with the reflected laser. In addition, increasing the laser intensity will directly enhance positron generation. This investigation will further facilitate high-flux positron generation and application.</p>